[en] The current main neurochemical theories of the biological correlates of suicidal behavior involve serotonergic and, to a lesser extent, dopaminergic systems. Few data are available about the possible implication of the noradrenergic function. In the present study, we assessed the growth hormone response to clonidine, a selective alpha 2-adrenergic agonist, in 15 DSM-III-R major depressive inpatients with a history of suicide attempts, compared with 15 age- and gender-matched major depressive inpatients without a history of suicidal behavior. Mean (+/- SD) growth hormone peak responses to clonidine were significantly lower in the group of suicide attempters than in the control group: 2.93 +/- 3.01 ng/ml vs. 8.28 +/- 8.15 ng/ml. Therefore, these results suggest that a blunted growth hormone response to clonidine could be a biological correlate of suicidal behavior.